Engine Response Adjustment Based on Traffic Conditions

ABSTRACT

A method for controlling an engine of a vehicle in response to an operator input, comprising of during a first non-cruise control condition and at first distance to a forward vehicle, adjusting engine output in response to said operator input with a first relationship; and during a second non-cruise control condition and at second, greater, distance to a forward vehicle, adjusting engine output in response to said operator input with a second relationship different from said first.

BACKGROUND AND SUMMARY

Vehicles systems receive various operator commands in order tofacilitate operator control of the powertrain, including an acceleratorfoot pedal input. Further, the relationship between the amount ofoperator depression and the powertrain response can be tuned to providedifferent drive feel and performance, and can be adjusted based onvarious engine or vehicle operating conditions. However, there may beconflicting goals in tuning the pedal relationship to vehicle outputresponse based on numerous factors.

For example, a higher gain relationship may be desired for some lowerpedal depression and/or lower vehicle speed conditions to provide a more“peppy” vehicle feel. This can be especially true when a vehicle isdesigned with a more under-powered powertrain in order to increase fueleconomy and/or reduce emissions. In other words, a smaller engine and/orotherwise adjusted transmission may provide improved fuel economy, butmay feel sluggish during acceleration driver tip-ins from lower speeds.

On the other hand, a lower gain relationship may be desired for otherlower pedal depression and/or lower vehicle speed conditions to providefiner engine and/or vehicle output torque control to give the operatorimproved ability in torque selection and adjustment. This can beespecially true during driving maneuvers under increased trafficconditions and/or during maneuvers such as vehicle parking or traversingrough terrain.

These and other issues may be at least partially resolved by adjusting arelationship between pedal input and vehicle output using an indicationof environmental and/or traffic conditions. For example, by consideringa distance to a forward vehicle indicative of vehicle trafficconditions, the gain may be adjusted to enable both a peppy feel duringlower traffic conditions and a finer torque selection during highertraffic conditions. The distance to a forward vehicle may be provided byinformation already available in some adaptive cruise control systems,and thus such information may advantageously be used even duringnon-cruise control conditions.

Likewise, a driver may select also provide some selectivity based on adesired fuel economy performance, such as through a driver selectablefuel economy switch, as to how the gain is adjusted in response to suchinformation, thereby providing gain adjustment that is more sensitive todriver needs and/or goals. In one embodiment, by integrating gainadjustment using both environmental information and driver selectablefuel economy information, it may be possible to provide improveddrivability over a variety of conditions while providing the operatorwith desired fuel economy performance in a smooth and coordinated way.

Note that the relationship between driver pedal input and vehicle and/orengine output may be adjusted in a variety of ways, including graduallyadjusting the relationship over time, as well as further adjusting therelationship based on various operating parameters such as engine speed,vehicle speed, gear ratio, etc. Further, gain adjustment may includeadjusting software-based transfer functions, algorithms, analogcircuitry, signal processing, and/or combinations thereof.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic depiction of an exemplary embodiment of an engineaccording to the present disclosure.

FIGS. 2-4 are example flow diagrams of various actions that may beperformed; and

FIGS. 5-8 are graphs illustrating various performance impacts overvarious operating conditions of pedal gain adjustments and driverselectable fuel economy modes.

DETAILED DESCRIPTION

FIG. 1 shows a schematic diagram of one cylinder of multi-cylinderinternal combustion engine 10. Combustion chamber or cylinder 30 ofengine 10 is shown including combustion chamber walls 32 and piston 36positioned therein and connected to crankshaft 40. A starter motor (notshown) may be coupled to crankshaft 40 via a flywheel (not shown).Cylinder 30 may communicate with intake port 44 and exhaust port 48 viarespective intake valve 52 and exhaust valve 54. Intake valve 52 andexhaust valve 54 may be actuated via intake camshaft 51 and exhaustcamshaft 53. Further, the position of intake camshaft 51 and exhaustcamshaft 53 may be monitored by intake camshaft sensor 55 and exhaustcamshaft sensor 57 respectively. Intake and/or exhaust valve control mayalso be provided by signals supplied by controller 12 via electric valveactuation (EVA). Additionally intake and exhaust valves may becontrolled by various other mechanical control systems including camprofile switching (CPS), variable cam timing (VCT), variable valve lift(VVL), and/or variable valve timing (VVT). In some embodiments, a valvecontrol strategy may include a combination of two or more of the abovementioned control techniques. While cylinder 30 is shown having only oneintake valve and one exhaust valve, it should be appreciated that insome embodiments cylinder 30 may have two or more intake and/or exhaustvalves.

Fuel injector 66 is shown coupled to intake port 44 for deliveringinjected fuel in proportion to the pulse width of signal FPW receivedfrom controller 12 via electronic driver 68. Fuel may be delivered tofuel injector 66 by a fuel system (not shown) including a fuel tank,fuel pumps, and a fuel rail. Engine 10 is described herein withreference to a gasoline burning engine, however it should be appreciatedthat in some embodiments, engine 10 may be configured to utilize avariety of fuels including gasoline, diesel, alcohol, and combinationsthereof.

Intake port 44 is shown communicating with intake manifold 42 viathrottle plate 64. Further, throttle plate 64 may be coupled to electricmotor 62 such that the position of throttle plate 64 may be controlledby controller 12 via electric motor 62. Such a configuration may bereferred to as electronic throttle control (ETC), which may be utilizedduring idle speed control as well.

Distributorless ignition system 88 may provide ignition spark tocombustion chamber 30 via spark plug 92 in response to spark advancesignal SA from controller 12. Though spark ignition components areshown, engine 10 (or a portion of cylinders thereof) may not includespark ignition components in some embodiments and/or may be operatedwithout requiring a spark.

Engine 10 may provide torque to a transmission system (not shown) viacrankshaft 40. Crankshaft 40 may be coupled to a torque converter whichis also coupled to a transmission via a turbine shaft. Torque convertermay include a bypass, or lock-up clutch. The lock-up clutch may beactuated electrically, hydraulically, or electro-hydraulically, forexample. The transmission may comprise an electronically controlledtransmission with a plurality of selectable discrete gear ratios.Alternatively, in some embodiments, the transmission system may beconfigured as a continuously variable transmission (CVT), or a manualtransmission.

Exhaust gas sensor 126 is shown coupled to exhaust port 48 upstream ofcatalytic converter 70. It should be noted that sensor 126 maycorrespond to a plurality of various different sensors and catalyticconverter 70 may correspond to a plurality of various emissions devicespositioned in the exhaust, depending on the exhaust configuration.Sensor 126 may be a sensor for providing an indication of exhaust gasair/fuel ratio such as an exhaust gas oxygen (EGO) sensor, linear oxygensensor, an UEGO, a two-state oxygen sensor, a HEGO, or an HC or COsensor. For example, a higher voltage state of signal EGO indicates thatexhaust gases may be rich of stoichiometry and a lower voltage state ofsignal EGO indicates that exhaust gases may be lean of stoichiometry.Further, signal EGO may be used during air/fuel control in order toestimate and validate various aspects of a desired engine control mode.

As described above, FIG. 1 merely shows one exemplary cylinder of amulti-cylinder engine, and that each cylinder has its own set ofintake/exhaust valves, fuel injectors, spark plugs, etc. Furthermore,although the above described engine is shown with a port injectionconfiguration, it should be appreciated that an engine may be configuredto inject fuel directly into the cylinders.

Controller 12 is schematically shown in FIG. 1 as a microcomputer,including microprocessor unit (CPU) 102, input/output ports 104, anelectronic storage medium, (ROM) 106, random access memory (RAM) 108,keep alive memory (KAM) 110, and a data bus. Controller 12 is shownreceiving various signals from sensors coupled to engine 10, in additionto those signals previously discussed, including measurement of inductedmass air flow (MAF) from mass air flow sensor 120 coupled to intakemanifold 42; engine coolant temperature (ECT) from temperature sensor112 coupled to cooling sleeve 114; a profile ignition pickup signal(PIP) from Hall effect sensor 118 coupled to crankshaft 40; and throttleposition TP from throttle position sensor in electronic motor 64; andabsolute Manifold Pressure Signal MAP from sensor 122. A pedal positionindication (PP) may be determined by a pedal position sensor 134 thatsenses the angle of pedal 130 according to driver input 132. Enginespeed signal RPM may be generated by controller 12 from signal PIP andmanifold pressure signal MAP from a manifold pressure sensor provides anindication of vacuum, or pressure, in the intake manifold. Controller 12may control the amount of fuel delivered by fuel injector 66 so that theair/fuel mixture in cylinder 30 may be selected to be at stoichiometry,a value rich of stoichiometry or a value lean of stoichiometry. In someembodiments, controller 12 may control the amount of fuel vapors purgedinto the intake port via a fuel vapor purge valve (not shown)communicatively coupled thereto. Further, in some embodiments, engine 10may include an exhaust gas recirculation (EGR) system that routes adesired portion of exhaust gas from exhaust port 48 to intake port 44via an EGR valve (not shown). Alternatively, a portion of combustiongases may be retained in the combustion chambers by controlling exhaustvalve timing.

Controller 12 may also perform cruise control operations when set by thevehicle operator. In one example, the system may include IntelligentCruise Control (ICC, which may also be referred to as Adaptive CruiseControl, ACC) operation in which throttle operation and vehicle speedcontrol, as well as brakes of a vehicle braking system 98, may becontrolled in response to various operating parameters. In one exampleembodiment, the operator may set a desired vehicle speed and activatethe cruise control system via coordinated action of pedal 130 and/orcruise control input devices 96. Then, the system may adjust engineoutput (e.g., via throttle 62, spark timing of plug 92, air-fuel ratio,etc.) and/or transmission states to maintain the desired vehicle speed.Further, the desired vehicle speed or vehicle operation may beinterrupted in response a distance between another vehicle or otherobject in front of the vehicle measured by distance sensor 94. Sensor 94may be use radar, sonar, laser measurements, or various other approachesto obtain a measure of distance to a forward vehicle or other object.Further, sensor 94 may also provide an indication of the speed of aforward vehicle, as well as its distance away. As such, the vehiclecontrol system may intentionally reduce engine output and/or adjusttransmission operation to reduce vehicle speed below the operator speedset-point when distance to a forward vehicle becomes less than a minimumvalue. Further, the system may use a combination of distance, vehiclespeeds (e.g., forward vehicle speed and speed of the vehicle beingcontrolled), and various other conditions to adjust or reduce vehiclespeed and/or engine output torque.

However, in addition cruise control operation, information about thetraffic conditions of the vehicle (such as the distance to a forwardvehicle) may also be used to adjust operation during non-cruise controlconditions. In one example, the distance to a forward vehicle may beused to adjust the engine torque response to operator pedal inputsduring low speed operating conditions. For example, during low speedvehicle operation where a forward vehicle is less than a selecteddistance away, the sensitivity of engine torque response to pedaldepression may be de-tuned to allow greater operator control andresolution of engine or vehicle output torque.

In another example, the distance to a forward vehicle, as well as therate of change of the distance may be used with other inputs to estimatedriving conditions. For example, stop-and-go city driving may bedistinguished from highway or freeway cruising by using a combination ofinputs, such as, for example, steering wheel angle and/or activity,pedal and/or brake actuation frequency and amplitude, vehicle speed,distance to a forward vehicle, speed of a forward vehicle, etc. Then,during selected conditions, the sensitivity of engine torque response topedal depression may be adjusted to allow greater operator control andresolution of engine or vehicle output torque during city stop-and-godriving as compared with higher speed steady speed operation.

In yet another embodiment, the amount of adjustment to the gain betweenpedal actuation and engine/vehicle output may be further based on adriver mode setting, such as a fuel economy mode or performance mode setby operator input device 90. While in one example only two modes may beselected, in another example, a plurality of modes ranging from economyto performance may be selected. In one example, the pedal gain may bede-tuned during the economy mode compared to the performance mode to agreater extent (or only) when a minimum measured distance to a forwardvehicle is reached.

Further still, various other examples of system operation are describedherein. In particular, additional details of control routines areincluded below which may be used with various engine configurations,such as those described in FIG. 1. As will be appreciated by one ofordinary skill in the art, the specific routines described below in theflowcharts may represent one or more of any number of processingstrategies such as event-driven, interrupt-driven, multi-tasking,multi-threading, and the like. As such, various acts or functionsillustrated may be performed in the sequence illustrated, in parallel,or in some cases omitted. Likewise, the order of processing is notnecessarily required to achieve the features and advantages of theexample embodiments of the invention described herein, but is providedfor ease of illustration and description. Although not explicitlyillustrated, one of ordinary skill in the art will recognize that one ormore of the illustrated acts or functions may be repeatedly performeddepending on the particular strategy being used. Further, these figuresmay graphically represent code to be programmed into the computerreadable storage medium in controller 12.

FIGS. 2-4 show flow diagrams depicting a method for controlling engineoperation in response to driver pedal actuation during both cruisecontrol conditions and non-cruise control conditions.

Referring now to FIG. 2, a routine is described for adjusting engineoutput via an adjustable relationship with pedal actuation. First, in210, the routine reads the selected or current relationship betweenpedal depression and a desired engine and/or vehicle output, which mayinclude a desired torque, acceleration, speeds, or combination thereof.Further details of the determination, selection of, and/or adjustment ofthe relationship are described with regard to FIGS. 3-4. While variousrelationships may be used, the routine may use a transfer function tomap pedal depression to desired output across various operatingconditions. Further, in addition or in an alternative, a pedal gainfunction may be as or to adjust a relationship between pedal input andthe output.

Continuing with FIG. 2, in 212 the routine reads a current pedalposition as actuated by the vehicle operator. For example, the routinemay read the current pedal position depression (PP) from sensor 34.Input filtering, noise filtering, and/or other signal processing mayalso be used to process the pedal depression reading.

Next, in 214, the routine determines the desired engine output torquebased on the pedal position of 212. Further, various other operatingparameters may be used to determine the desired engine torque such as,for example, engine speed, vehicle speed, barometric pressure, ambienttemperature, gear ratio, and/or race other parameters. Next, in 216, theroutine determines the desired throttle position based on the desiredengine output torque and current operating conditions. In one particularexample, the routine may determine desired throttle position based onthe desired engine torque, engine speed, and engine coolant temperature.While the throttle is used in this example to adjust engine outputtorque, various other engine actuators may be used. For example,alternative or additional actuation may be used to adjust engine torque,such as, for example, valve events, valve lift, boosting, valve timing,fuel mass and air-fuel ratio, spark timing, injection timing, orcombinations thereof can be used.

Then, in 218, the routine adjusts the electronic throttle to arrive atthe desired throttle position. In this way, the engine throttle may beadjusted in response to the operator command taking into account currentand various other operating conditions using the selected mapping of210.

Various other approaches may also be used to adjust engine output and/orengine throttle angle. In one example alternative embodiment, theroutine may identify a desired throttle position directly in response tothe pedal position and relationship of 210.

In either case, the routine electronically controls the throttleposition in response to the operator pedal actuation to provide adesired response characteristic via the gain/transfer function 210. Asdescribed herein, various adjustments to the gain/transfer function maybe used based on various conditions, including the distance to a forwardvehicle. Such operation may be used to enable higher gain during lesscongested traffic conditions to provide improved driver perception ofengine performance, while enabling a reduced gain during higher trafficcongestion to enable greater engine output torque and/or vehicle outputtorque resolution for the operator.

Referring now specifically to FIG. 3, a routine is described fordetermining whether and how to adjust the gain/transfer function betweenthe pedal position and the desired torque or desired throttle position.First, in 310, the routine determines whether pedal gain/transferfunction adjustment is enabled. In one example, gain adjustment may beenabled during selected conditions, such as during low vehicle speedand/or low engine speed conditions (e.g., speeds below a thresholdvalue). Alternatively, pedal gain adjustment may be enabled after avehicle warm-up condition, such as after engine coolant temperature hasreached a threshold value. Further, various other conditions may beutilized to enable pedal gain adjustment.

When the answer to 310 is yes, the routine continues to 312 to determinewhether cruise control is activated. For example, the routine maydetermine whether a cruise control system is enabled via a userselectable switch such as 96. Alternatively, the routine may determinewhether a cruise control system is in an ON state. Further still, theroutine may determine whether cruise control is currently overriding oradjusting engine torque and/or vehicle speed to provide a desiredvehicle speed set by the vehicle operator. In one particular example,the routine determines whether an operator is currently overriding acruise control set point, or whether the cruise control system has beendisabled by the vehicle operator. When the cruise control system isactive, the routine continues to 314 to maintain the current pedalgain/transfer function at its current setting. Otherwise, when theanswer to 312 is no, the routine continues to 316.

In 316 through 322, the routine utilizes sensors and/or otherinformation from the cruise control system to adjust the pedalgain/transfer function to provide improved vehicle drivability andperformance during non-cruise control conditions. First in 316, theroutine reads a distance to a forward vehicle, if any, and a currentmode selection. For example, the routine may read a performance and/orfuel economy mode selected via driver selectable switch 90. Further, theroutine may read a distance to a forward vehicle from sensor 94. Next,in 318, the routine processes the readings 316 and other operatingconditions to correlate these to an estimate of current drivingenvironment conditions. For example, the routine may estimate whethercurrent conditions represent city stop-and-go driving conditions, oralternative driving conditions. As noted herein, the routine may furtherinclude information other than or in addition to the distance to aforward vehicle and a current mode selection, including a number ofactuations of the vehicle pedal and/or brakes, steering angle, steeringand/or braking history, vehicle speed, and/or various other conditions.Next, in 320, the routine determines the pedal gain/transfer functionbased on the driving conditions and other operating inputs. For example,the routine may de-tune one or more regions of the gain/transferfunction between pedal position and the desired torque or throttleposition in response to the distance to a forward vehicle, a driver modeselection, and/or various operating conditions including vehicle speed,engine speed, etc. Then, in 322, the routine adjusts/transitions thegain/transfer function at an appropriate timing or condition and in anappropriate manner as described down below herein with further referenceto FIG. 4.

In this way, it is possible to adjust the driver's perceived performanceof the vehicle via an engine output to pedal actuation relationshipbased on various conditions including traffic congestion, vehicle speed,and various others.

Referring now to FIG. 4, an example routine for transitioning/adjustingthe pedal gain/transfer function is described. First, in 410, theroutine determines whether an adjustment has been requested/determined.If so, the routine continues to 412 to monitor operating conditions.Then, in 414 the routine determines whether conditions are within aselected window to vary the gain/transfer function. In one example, theroutine may determine whether the pedal is at a closed pedal (released)position, as it is possible to vary the gain/transfer function duringsuch a condition with reduced driver perception. In another example, theroutine may determine whether sufficient modulation of the pedal by theoperator is being performed. In still another example, the routine maymonitor vehicle speed and engine speed conditions to enable adjustmentof the gain during lower speed conditions. Further still, various otherselected windows may be used to vary the gain/transfer function.

If such conditions are identified in 414, the routine continues to 416to adjust the gain/transfer function. In one example, the gain/transferfunction may be adjusted over a predetermined time or number of engineoperating cycles. For example, a filtering may be used to provide slowervariation in adjustment of the throttle response in response to thegain/transfer function adjustment. In this way, the pedal gain can beadjusted in a selected way during selected conditions to enable improveddriver performance.

Referring now to FIG. 5, an example graph illustrates differentvariations in the pedal mapping for operating modes, including a driverselected performance/economy mode and/or the ICC mode. In this example,different initial gains are provided for ICC operation and non-ICCoperation, as well as different initial gains for theperformance/economy mode selected. As noted herein, these gains may befurther adjusted based on driving conditions, such as a distance to aforward vehicle, vehicle speed, and/or traffic conditions.

In particular, referring now to FIG. 6, an example graph illustratesvariation in the pedal mapping in one particular mode for varyingtraffic conditions, in particular, for varying distance to a forwardvehicle. Specifically, FIG. 6 shows an example transfer function betweenpedal position (from closed pedal to wide-open pedal) to desired engineoutput torque or throttle position. As shown, at higher distances to aforward vehicle (e.g., no forward vehicle or reduced traffic at highervehicle speeds) during lower pedal positions a higher gain is provided(e.g., a greater slope at lower pedal position than higher pedalpositions). However, as the traffic increases, or the distance to aforward vehicle decreases, and/or vehicle speed decreases, the gain atlower pedal positions decreases while the gain at higher pedal positionsincreases. In this way, a substantially continuous relationship betweenclosed pedal and wide-open pedal can be maintained while still providingvariable gain.

However, note that in an alternative embodiment, shown in FIG. 7, thegain may be varied in a specified region as well. Specifically, greateradjustment (e.g., de-tuning) may be provided at lower pedal positionswhile providing a more consistent response at higher pedal positions.

Referring now to FIG. 8, the adjustment to the pedal gain is illustratedvia an adjustment (reduction) factor applied to the gain/transferfunction. Specifically, FIG. 8 illustrates how the adjustment/reductionmay vary depending on conditions such as a distance to a forward vehicleand a driver selected vehicle performance/economy mode. Again, thisexample illustrates one possible approach, and the x-axis may includevarious parameters, including a combination of an indication of trafficcongestion, vehicle speed, distance to a forward vehicle, etc.

In this way, the pedal to vehicle response gain may be varied to providea driver finer torque resolution at lower speeds when other vehicles arein close proximity, while still providing a high performance responseduring other operating conditions.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and nonobvious combinationsand subcombinations of the various systems and configurations, and otherfeatures, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsubcombinations regarded as novel and nonobvious. These claims may referto “an” element or “a first” element or the equivalent thereof. Suchclaims should be understood to include incorporation of one or more suchelements, neither requiring nor excluding two or more such elements.Other combinations and subcombinations of the disclosed features,functions, elements, and/or properties may be claimed through amendmentof the present claims or through presentation of new claims in this or arelated application. Such claims, whether broader, narrower, equal, ordifferent in scope to the original claims, also are regarded as includedwithin the subject matter of the present disclosure.

1. A method for controlling an engine of a vehicle in response to anoperator input, comprising: during a first non-cruise control conditionand at first distance to a forward vehicle, adjusting engine output inresponse to said operator input with a first relationship; and during asecond non-cruise control condition and at second, greater, distance toa forward vehicle, adjusting engine output in response to said operatorinput with a second relationship different from said first.
 2. Themethod of claim 1 wherein said operator input is actuation of a footpedal.
 3. The method of claim 1 wherein said second condition includes ahigher vehicle speed than said first condition.
 4. The method of claim 1further comprising adjusting said first and second relationships inresponse to a driver selectable performance or fuel economy mode.
 5. Themethod of claim 1 wherein said engine output includes an engine torqueoutput, and said engine output torque is adjusted by varying at leastone of a fuel injection amount, valve timing, injection timing, andair-fuel ratio.
 6. The method of claim 1 wherein said engine output isadjusted by a throttle position of an electronically controlled throttleplate.
 7. The method of claim 1 further comprising during a third cruisecontrol condition, adjusting engine output in response to an operatorspeed set-point.
 8. The method of claim 1 wherein said differenceincludes an increased gain between said operator input an engine outputat said second distance.
 9. A method for controlling an engine of afirst vehicle in response to an operator pedal input, comprising:varying a relationship between pedal position and engine output inresponse to distance to a second vehicle, vehicle speed of the firstvehicle, and a driver selectable performance mode during non-cruisecontrol conditions.
 10. The method of claim 9 wherein said relationshipis varied to have a greater gain between pedal motion and engine torqueduring lower speed conditions where said distance is greater than afirst threshold value and the driver has selected a higher performancemode.
 11. The method of claim 10 wherein said relationship is varied tohave a smaller gain between pedal motion and engine torque during lowerspeed conditions where said distance is less than a second thresholdvalue and the driver has selected a higher fuel economy mode.
 12. Asystem for a first vehicle having a powertrain with an engine,comprising: an intelligent cruise control system selectively controllingvehicle speed in response to an operator set-point during active cruisecontrol conditions, said system further providing an indication of aspatial relationship between the first vehicle and the second vehicleand overriding said set-point in response to said spatial relationship;an pedal adapted to receive a command from the vehicle operator; and acontroller for varying a response of powertrain output in response toactuation of the pedal, where said relationship is adjusted duringvehicle operation in response to said spatial relationship duringin-active cruise control conditions.
 13. The system of claim 12 whereinsaid spatial relationship includes a distance between the first andsecond vehicle.
 14. The system of claim 12 wherein said spatialrelationship includes velocities of the first and second vehicle. 15.The system of claim 12 wherein said spatial relationship includesrelative velocities of the first and second vehicle
 16. The system ofclaim 12 wherein said relationship is adjusted to a greater extent atlower pedal positions than at higher pedal positions.
 17. The system ofclaim 12 wherein said relationship is adjusted to a greater extent atmid pedal positions.
 18. The system of claim 12 wherein saidrelationship is adjusted at selected conditions including a closed pedalcondition.
 19. The system of claim 18 further comprising anelectronically controlled throttle plate, and where said relationshipchanges a response between pedal actuation and position of the enginethrottle plate.
 20. The system of claim 19 wherein said in-active cruisecontrol conditions include operating at vehicle speeds less than athreshold value.